Non-conventional synthesis and photophysical studies of platinum(ii) complexes with methylene bridged 2,2'-dipyridylamine derivatives

Synthesis and crystal structure of tetra-methyl (E)-4,4'-(ethene-1,2-di-yl)bis-(5-nitro-benzene-1,2-di-carboxyl-ate)

The title compound, C22H18N2O12, was obtained as a by-product during the planned synthesis of 1,2-bis-(2-nitro-4,5-dimethyl phthalate)ethane by oxidative dimerization starting from dimethyl-4-methyl-5-nitro phthalate. To identify this compound unambiguously, a single-crystal structure analysis was performed. The asymmetric unit consists of half a mol-ecule that is located at a centre of inversion. As a result of symmetry restrictions, the mol-ecule shows an E configuration around the double bond. Both phenyl rings are coplanar, whereas the nitro and the two methyl ester groups are rotated out of the ring plane by 32.6 (1), 56.5 (2) and 49.5 (2)°, respectively. In the crystal, mol-ecules are connected into chains extending parallel to the a axis by pairs of C-H⋯O hydrogen bonds that are connected into a tri-periodic network by additional C-H⋯O hydrogen-bonding inter-actions.

Chemistry on the Complex: Derivatization of TiO4 N2 -Based Complexes and Application to Multi-Step Synthesis

The chemistry on octahedral TiO₄ N₂ -complexes is described. The Ti(IV)-based precursors are composed of two 3,3'-diphenyl-2,2'-biphenolato ligands (1) and one substituted 1,10-phenanthroline ligand (2-5). The application of imine condensation, palladium-catalyzed C-C bond formation or copper-catalysed azide-alkyne cycloaddition allowed the grafting of various new groups onto these species. In particular Sonogashira reactions permitted to observe an excellent conversion of the starting complexes. This systematic study enabled to compile the factors required to preserve the framework of the complexes in the course of a chemical transformation. Thanks to this chemistry realized on the complex, the Ti(1)₂ fragment was used as a protecting group to develop a multi-step synthesis of a bis-phenanthroline compound (12), for which the synthesis without this protection failed. Thus, a dinuclear complex [Ti₂ (1)₄ (12)] was first prepared starting from complex precursor bearing an acetylenic function via a Hay coupling reaction. This was followed by a deprotection step affording 12. Overall, this work illustrates how the Ti(1)₂ fragment could be an useful tool for the preparation of unprecedented diimine compounds.

Noncovalent Axial I⋅⋅⋅Pt⋅⋅⋅I Interactions in Platinum(II) Complexes Strengthen in the Excited State

Coordination compounds of platinum(II) participate in various noncovalent axial interactions involving metal center. Weakly bound axial ligands can be electrophilic or nucleophilic; however, interactions with nucleophiles are compromised by electron density clashing. Consequently, simultaneous axial interaction of platinum(II) with two nucleophilic ligands is almost unprecedented. Herein, we report structural and computational study of a platinum(II) complex possessing such intramolecular noncovalent I⋅⋅⋅Pt⋅⋅⋅I interactions. Structural analysis indicates that the two iodine atoms approach the platinum(II) center in a "side-on" fashion and act as nucleophilic ligands. According to computational studies, the interactions are dispersive, weak and anti-cooperative in the ground electronic state, but strengthen substantially and become partially covalent and cooperative in the lowest excited state. Strengthening of I⋅⋅⋅Pt⋅⋅⋅I contacts in the excited state is also predicted for the sole previously reported complex with analogous axial interactions.

N,N-bis(2-quinolinylmethyl)benzylamine

N,N-bis(2-quinolinylmethyl)benzylamine (1) was synthesized under basic conditions from a pseudo-three-component reaction between benzylamine and two molecules of 2-(quinolinylmethyl)chloride, resulting in the formation of two N–C bonds in a single step. Compound (1) crystallizes in the triclinic system of the P-1 space group. The unit cell comprises a dimer of 1, in which the monomers are linked by two complementary hydrogen bonds between N1 and H′1–C′1 of another molecule. The dimers form chains along the a-axis through intermolecular interactions between the N′2 acceptor atoms and C″17 donors from molecules in the nearest neighboring dimer. These interactions form extended sheets of the dimers of 1, along the ab plane. The quinolinylmeth-2-yl groups of 1 lie in almost orthogonal planes and their N1/2(q) donor atoms are away from the apical amino N3 atom.